1. Field of the Invention
The present invention relates to a material feeding apparatus, and particularly to an apparatus which intermittently feeds a material such as a sheet material, a wire material and the like to a working machine such as a press machine and the like at every fixed amounts.
2. Description of the Related Art
As an apparatus which feeds a material such as a sheet material, a wire material and the like to a working machine such as a press machine and the like, for example, Japanese Utility Model Examined Publication 60-27549 has been conventionally known. The apparatus is provided with a first gripper apparatus structured such as to perform a material clamping (gripping) operation and a material unclamping (releasing) operation between a first stationary gripper and a first movable gripper, and a second gripper apparatus disposed on a sliding block capable of oscillating along a transfer path of the material and structured such as to perform material clamping and unclamping operations between a second stationary gripper and a second movable gripper, and performs the material clamping and unclamping operation and the sliding block sliding operation by means of the first and second gripper apparatuses at a predetermined timing with using a cam apparatus, a swinging arm and the like.
In this case, since the apparatus is structured such as to control both of the first gripper and the second gripper by the single swinging arm which is swung by the single cam so as to perform the material clamping and unclamping operation by the first gripper apparatus and the second gripper apparatus, there has been a problem that it is hard to suitably set a timing of the operation of the first gripper apparatus and the second gripper apparatus. Particularly, it is impossible to design such that both of the first and second gripper apparatuses temporarily clamp the material at a starting time and a finishing time of each one of the material intermittent feedings, whereby the material is prevented from becoming a free state, so that it is hard to improve a feeding accuracy and make the feeding high-speed.
Then, in order to solve the problem, the applicant of the present application proposed Japanese Patent Unexamined Publication No. 63-82271. This apparatus respectively drives the first and second gripper apparatuses and the sliding block by independent cams so as to prevent a free state in which the material is not fully clamped from being generated during all the period of the material feeding operation, thereby making a high-speed and high-accuracy material feeding possible.
However, even the apparatus proposed by the applicant can not always satisfy a requirement with respect to the feeding accuracy and the feeding speed which have been required for this kind of feeding apparatus in recent days.
That is, in recent years, electronic information devices such as a portable telephone, a personal computer and the like are significantly spread, however, while these devices become compact and inexpensive, in a production field, in order to correspond to making parts compact and high-density, a feeding (a positioning of the material) at significantly higher accuracy than the conventional one is going to be desired. Further, in order to satisfy the requirement for improving a productivity, reducing a cost, mass production and the like, it is desired to provide an apparatus which can be operated at higher speed.
For example, in a press working industry, a requirement with respect to a high-speed operation has been increased year by year, and there is provided a press machine which can operate at two or three times higher speed than that of the conventional apparatus proposed by the applicant. However, in a current status, a feeding apparatus for supplying a material to the press machines does not always correspond to the operation speed of the press machine.